A classic barrel roll could be demonstrated in the B757/767 Sim but, strangely enough, was never tempted to try it in the aircraft
However, the smoothest barrel roll I ever sat in on was demonstrated by the late Neil Williams (British Aerobatic Chmpion at the time) in a Falcon fanjet. He had two passengers standing in the back drinking champagne but as it was night they never realised they had been upside down.
Wasn't close enough to see whether the direction of the bubbles was affected!